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Yesterday's ADAP describes the variable baseline interferometer,
used at the Parkes Observatory in the late 1960s and early 1970s,
which combined the signals from the 18m (60-foot) "Kennedy" antenna
(Giyalung Guluman) and the 64m (210-foot) Dish (Murriyang).
This innovative system allowed the one-dimensional structure of
radio sources to be determined in about
15 minutes, as opposed to the months required by fixed-spacing
interferomemters elsewhere.
The image above is a variable baseline visibility record of
the double-lobed radio galaxy Pictor A
showing the fringes and the classic double-source amplitude modulation.
The x-axis is the baseline length in feet, with the amplitudes at
two frequencies (467 and 1401MHz), measured simultaneously, plotted.
(Ron gives more details of the variable baseline interferometer in
a video available from the
Parkes 60th webpage.)
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